Process of purifying diphenyl-1, 2, 5, 6-anthraquinone dithiazole bodies



Patented Dec. 20, 1932 Unite STATES,

PATENT OFICE. 9

WILLIAM L. RINTELMAN, OF MILWA'O'KEE, WISCONSIN, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO E. I. DU FONT DE NEE/TOURS & COMPANY, A CORPORATION OF DELAWARE PROCESS OF PURIFYING DIPHENYL-1,2,5,6-ANTHRAQUINONE DITI-IIAZOLE BODIES No Drawing.

This invention relates to a process of purifying diphenyl-1,2,5,6-anthraquinone-dithiazole bodies.

More specifically this invention relates to a process of purifying diphenyl-1,2,5,6-anthraquinone-dithiazole, diphenyl-1,2,5,6-anthraquinone-dithiazoline, and mixtures of the two.

The preparation of compounds of this type, which are valuable yellow dyestuffs, has been described in U. S. Patents 1,090,621 and 1,095,731; The earlier of these patents suggests the purification of the dyestufi by recrystallization from boiling nitrobenzene. Although this patent also discloses the property of the dyestufi' of dissolving in concentrated sulfuric acid. and being precipitated therefrom by means of water, it has not been appreciated that this property may be taken advantage of to effect separation of the dyestuff from its impurities and to isolate the highly pure dyestulf in a greener and brighter shade than was obtainable from nitrobenzene recrystallization.

Ihave now foundthat by suitably regulating the concentration of the sulfuric acid, diphenyl -1,2,5,6 anthraquinone dlthiazole bodies may be effectively separated from their impurities. Moreover, the dyestufi thus obtained is purer,exhausts more cleanly, and gives greener and brighter shades upon cotton than when purified from nitrobenzene. Furthermore, my novel process is more economical than the .old nitrobenzene process, providing, of course, that undue losses of the dyestuff are avoided in carrying out the process as more fully set forth below.

' It is therefore an object of this invention to provide a simple and efiicient process of purifying diphenyl 1,2,5,6 anthraquinonedithiazole bodies. c c

I It is a further object of this invention to obtain 1,2,5,6 anthraquinone-dithiazole bodies in a highly pure state.

Other and further important objects of this invention will become apparent from the following description and appended claims.

I have found that with an average crude dyestufi the optimum'concentration of sulfuric acid for my process is about 83 to 87%.

Application filed April 20, 1931. Serial No. 531,635..

If the concentration is allowed todrop below 80%, some of the impurities will be precipitated along with the dyestufit', thereby defeat ing the object of the process. If a concentration above 90% is selected, a substantial portion of the dyestuff stays in solution, thus rendering the process uneconomical unless practiced by a repeated or cyclic system using the mother liquor to purify the next batch. A simpleprocedure to follow in regulating the concentration of the acid is to dissolve the dyestutl' in concentrated sulfuric acid of above 90% strength, and then add suficient water to reducethe concentration to about 85%.- A pure dyestuff is thus obtained with great efficiency. i

Instead of water, other diluents may be used, such as, for example, glacial acetic acid or dilute sulfuric acid. The novel purification process may be combined with the process of formation of the dyestuff where the reaction is carried out in concentrated sulfuric acid. In this case, the reaction mass is diluted to about sulfuric acid concentration, whereupon the dyestuif precipitates directly in a high state of purity and may be recovered by filtering and wash ing in the usual manner. Without limiting my invention to any particular procedure, the following examples in which parts by weight are given, will serve to illustrated form. c

'Emample 1.-10 parts of the crude diphenyl-1,2,5,6-anthraquinonadithiazole body as obtained, for instance, according to the process disclosed in either of U. S. Patents 1,090,621 and 1,095,731 or by condensing a 1,5- dimercapto-2,6-diamino-anthraquinone body with a body of the formula my method in its preferred whereinRis an aromatic carbocyclic ring, X is halogen or hydrogen and Y is oxygen .or two halogens in an inorganic medium as is more. fully described in copending application, Serial No. 531,636, filed by myself andRobert J. Goodrich of even date herewith, are dissolved in 150 parts of sulfuric acid monohydrate at a temperature of about 30 to 40 C. 127 parts of water are carefully dropped in and the mass is cooled to room temperature. The mixture is next filtered, washed with 50'parts of 83% sulfuric acid, and finally with water until free of acid. It is then sucked dry. The

p a filter cake upon drying constitutes the dyes stuff in ahigh state'of purity;

Example '2.l0 parts ofthe 1,5-sulfide de rivative of 2,6-diamino-anthraquinone, ob-

tainable, for instance, by passing a streanrof' air through an aqueous, alkaline solution of 1 =80.90 LC, and lstirred at this temperature the disodium salt of 1,5-dimercapto-2,6-diamino-anthraquinone as described more fully in my copending application, Serial No.

531,633, filed of even date herewith, are dis-. sol'ved'in 200 parts of sulfuric acidmonohydrate. The temperature of the solution'is adjusted'to about'35 to 45C. and 7.5 parts of 'benzaldehyde are then added and the reaction mass stirred at about 35 to45 C. for'aperiod of about hours. If desired, the temperaer. When the reaction is substantially complete, the mass is gradually diluted with Water to asulfuric acid concentration of about 7 85%, cooled to about .20 to (1., and the greenish yellow crystals which separate are filtered oif, and'washedfirst with 100 parts of 83% sulfuric acid, and then with water until free of acid. The dyestuff thus obtained-constitutes a. 1,2,5,6-anthraquinone diphenyl-di thiazole body ina statelof, high purity. 'Its dyeings upon cotton froma vat, producedin v the ordinary manner, exhibit great brilliance and-purityof shade;

Example 35-10 parts I of 1,5-dimerca to- 2,6-diamino-anthr aquinone-Vare dissolved in QOOparts of sulfuric acid monohydrate, and the temperature of the solution is adjusted to about 85 to G. 10 parts of benzaldehyde are now added and the reaction mass is stirred at about 35 to 45 C. for a period of about 20 hours. Highertemperaturesmay be used ,if

desired to speed up the reaction.- When'the reaction is .substantially complete, the. mass isgradually diluted with waterto a sulfuric acid concentrationof about85%, cooled .to about 20 to 25 (3 and the greenish yellow mass is stirred for l hour at'a'bout 25-30 (3.,

and then heatedgradu'ally during a period of about 1 hourfto 170C. and maintained atjthis' temperature for aboutz2 hours. The

mass is now cooled to about 25''35 -C. and 37 parts of water are gradually droppedin sulfuric acid; The filter cake is now sludged' up with 800partsof cold water, 'filtered,-and washed with cold water untilfree of'acid.

Upon drying [and grinding the' dyestufi (a 1,2,5,6 anthraquinone-diphenvl-dithiazole body) isobtainedina state of'high purity."

Emample 5.10] parts of a crude dyestuff as defined in Example 1' are susperrdedgin 170' parts of 85% sulfuric acid, .warmed to for about 3 hours. The mass is then slowly cooled to room temperature, and after stirring for another 6 hours the mass isfiltered, washed and dried .as. in Example 1. The

filterca'ke constitutes the dyestuff in-a state ofhighpurity, as in Example 1. In thisexample it is not necessary "to dissolve the entire dyestuif, since the impurities 'a're'ex tracted by means of the sulfuric acid;

Thus, although I have indicated aksulfuric acid concentration range of about.*83 to *87%.

as imcluding the preferred concentrations, this range merely indicates the optimum for crude dyestuff ofthe averagefpurity resulting from technical operation and concentrations above and below said'limits Qmayfbe used with satisfactory results on occasional batchesof crude dy'estufi. The operativeness of'a given concentrationof-sulfuric acid depends, to a considerable extent, upon the relative impurity of the dyestuif,-upon the ioo quantity 7 of sulfuric acid :used, and upon'the l temperature at which the process is carried out. Thus, if a sufiiciently large quantity of acid is used, a concentration of7'6% may'be effective to precipitate'the dyestufi' 'inpure form. Again, if the crudeydyestufi is rel'atively pure and 'i-f'little sulfuric acid is used,

93% sulfuric acid may be usedfor the above purpose withoutlosing too much dyestufi'. As pointed out above, in this case the saturated mother liquor after purification of a given quantity of dy'estufi' may be used to purify anotherquantityth-us avoiding possible waste of dyestuif due to its high solubilit i -93% sulfuric acid.

the thiazoline bodies. 7

. a v '115 The term diphenyl-l,2,'5,6-anthraquin I am; aware that numerous details 7 of the diphenyl- 1,2,5,6 anthraquinone' v dithiazole process may be varied throng-ha wide range 1 without departing from'the principles ofthis patent granted hereon otherwise .7

body which comprises treating the impure body with sulfuric acid having a concentration from about 76 to 937% and recovering the insoluble portion of the dyestuif.

2. The process of purifying an impure diphenyl 1 ,2 5 ,6 anthraquinone dithiazole body which comprises treating the impure body with sulfuric acid having a concentration of about 80 to 90%, and recovering the insoluble portion of the dyestufl'.

3. The process of purifying a technical diphenyl 1 ,2, 5 ,6 anthraquinone dithiazole body which comprises treating the same with sulfuric acid of about 83 to 87% concentration and recovering the insoluble portion of the dyestufi.

41. The process of purifying an impure diphenyl 1 ,2 5 ,6 anthraquinone dithiazole body which comprises crystallizing the same from sulfuric acid having a concentration of about 5. A process for preparing a yellow vat dyestulf in a state of high purity, which comprises condensing a 1,5 dimercapto- 2,6- diamino-anthraquinone body with benzaldehyde in a sulfuric acid medium of above 90% concentration, diluting the reaction mass to a sulfuric acid concentration of about 83 V to %7% and recoving the precipitated dyestu In testimony whereof I have hereunto subscribed my name at Carrollville, Milwaukee County, Wisconsin.

WILLIAM L. RINTELMAN. 

